First clinical and biomechanical results of the Trochanteric Fixation Nail (TFN)

Physicomechanical, morphological and tribo-deformation characteristics of lightweight WC/AZ31B Mg-matrix biocomposites for hip joint applications

Exploring high strength materials with a higher concentration of reinforcements in the alloy proves to be a challenging task. This research has explored magnesium-based composites (AZ31B alloy) with tungsten carbide reinforcements, enhancing strength for medical joint replacements via league championship optimisation. The primary objective is to enhance medical joint replacement biomaterials employing magnesium-based composites, emphasising the AZ31B alloy with tungsten carbide reinforcements. The stir casting method is utilised in the manufacture of magnesium matrix composites (MMCs), including varied percentages of tungsten carbide (WC). The mechanical characteristics, such as micro-hardness, tensile strength, and yield strength, have been assessed and compared with computational simulations. The wear studies have been carried out to analyse the tribological behaviour of the composites. Additionally, this study investigates the prediction of stress and the distribution of forces inside bone and joint structures, therefore offering significant contributions to the field of biomedical research. This research contemplates the use of magnesium-based MMCs for the discovery of biomaterials suitable for medical joint replacement. The study focuses on the magnesium alloy AZ31B, with particles ranging in size from 40 to 60 microns used as the matrix material. Moreover, the outcomes have revealed that when combined with MMCs based on AZ31B-magnesium matrix, the WC particle emerges as highly effective reinforcements for the fabrication of lightweight, high-strength biomedical composites. This study uses the league championship optimisation (LCO) approach to identify critical variables impacting the synthesis of Mg MMCs from an AZ31B-based magnesium alloy. The scanning electron microscopy (SEM) images are meticulously analysed to depict the dispersion of WC particulates and the interface among the magnesium (Mg) matrix and WC reinforcement. The SEM analysis has explored the mechanisms underlying particle pull-out, the characteristics of inter-particle zones, and the influence of the AZ31B matrix on the enhancement of the mechanical characteristics of the composites. The application of finite element analysis (FEA) is being used in order to make predictions regarding the distribution of stress and the interactions of forces within the model of the hip joint. This study has compared the physico-mechanical and tribological characteristics of WC to distinct combinations of 0%, 5%, 10% and 15%, and its impact on the performance improvements. SEM analysis has confirmed the findings' improved strength and hardness, particularly when 10%-15% of WC was incorporated. Following the incorporation of 10% of WC particles within Mg-alloy matrix, the outcomes of the study has exhibited enhanced strength and hardness, which furthermore has been evident by utilising SEM analysis. Using ANSYS, structural deformation and stress levels are predicted, along with strength characteristics such as additional hardness of 71 HRC, tensile strength of 140-150 MPa, and yield strength closer to 100-110 MPa. The simulations yield significant insights into the behaviour of the joint under various loading conditions, thus enhancing the study's significance in biomedical environments.

Comparison of Helical Blade Systems for Osteoporotic Intertrochanteric Fractures Using Biomechanical Analysis and Clinical Assessments

Background and Objectives: This study aimed to compare the biomechanical properties and outcomes of osteoporotic intertrochanteric fractures treated with two different helical blade systems, the trochanteric fixation nail-advanced (TFNA) and proximal femoral nail antirotation II (PFNA), to evaluate the efficacy and safety of the newly introduced TFNA system. Materials and Methods: A biomechanical comparison of the two helical blades was performed using uniaxial compression tests on polyurethane foam blocks of different densities. The peak resistance (PR) and accumulated resistance (AR) were measured during the 20 mm advancement through the test block. For clinical comparison, 63 osteoporotic intertrochanteric fractures treated with TFNA were identified and compared with the same number of fractures treated with PFNA using propensity score matching. Ambulatory status, medial migration, lateral sliding, fixation failure, and patient-reported outcomes were compared between the two groups over a minimum of 1 year's follow up. Results: The uniaxial compression test showed that a slightly, but significantly lower resistance was required to advance the TFNA through the test block compared with the PFNA (20 PCF, p = 0.017 and p = 0.026; 30 PCF, p = 0.007 and p = 0.001 for PR and AR, respectively). Clinically, the two groups showed no significant differences in post-operative ambulatory status and patient-reported outcomes. However, in TFNA groups, significantly more medial migration (TFNA, 0.75 mm; PFNA, 0.40 mm; p = 0.0028) and also, lateral sliding was noted (TFNA, 3.99 mm; PFNA, 1.80 mm; p = 0.004). Surgical failure occurred in four and two fractures treated with the TFNA and PFNA, respectively. Conclusions: The results of our study suggest that the newly introduced TFNA provides clinical outcomes comparable with those of the PFNA. However, inferior resistance to medial migration in the TFNA raises concerns regarding potential fixation failures.

The Utility of the Tip-Apex Distance in Predicting Axial Migration and Cutout With the Trochanteric Fixation Nail System Helical Blade

OBJECTIVES

To determine whether a tip-apex distance (TAD) <20 mm is associated with a higher rate of axial migration and perforation with the Trochanteric Fixation Nail (TFN) System helical blade implant.

DESIGN

Retrospective.

SETTING

Level I Trauma Center.

PARTICIPANTS

Four hundred forty-three patients surgically treated for proximal femur fractures were identified through a query of Current Procedural Terminology code 27245 from January 2009 to February 2013. A total of 258 patients treated with the TFN helical blade system were included in the study.

MAIN OUTCOME MEASURED

The association of axial migration and perforation with the measured TAD.

RESULTS

The overall rate of mechanical complications was 10.1%. The average TAD was 20.4 mm. Axial perforation occurred in 8 patients (3.4%). Axial migration up to subchondral bone without perforation occurred in 3 patients (1.1%). Only 1 fracture failed in varus (0.38%). There was a significant difference in the rates of combined axial migration and perforation with a TAD <20 mm (P = 0.03). Logistic regression model demonstrated increased odds for combined axial cutout and migration with TAD less than 20 (odds ratio = 1.15, P = 0.01).

CONCLUSIONS

A TAD <20 mm was associated with an increased frequency of axial migration and cutout with the TFN helical blade.

LEVEL OF EVIDENCE

Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

What is the optimal salvage procedure for cut-out after surgical fixation of trochanteric fractures with the PFNA or TFN?: A multicentre study

PURPOSE

To evaluate the outcome after different types of revision operations for blade 'cut-out' and 'cut-through' after fixation of trochanteric fractures with proximal femoral nail antirotation (PFNA) or a trochanter fixation nail (TFN).

METHODS

Twenty hospitals participated in this multicentre study. A total of 4109 patients were retrospectively screened for cut-out or cut-through complications after nailing of trochanteric fractures using PFNA or TFN. Fifty-seven patients (28 with 'cut-through' and 29 with 'cut-out') were included in the study. In the 'cut-through' group, 16 patients underwent a blade exchange, six patients had a blade exchange with bone cement augmentation, and six received total hip arthroplasty (THA). In the 'cut-out' group, three patients had a blade exchange, one had a blade exchange with augmentation, three underwent re-nailing of the fracture with a new PFNA, one had a girdlestone procedure and 21 had THA procedures.

RESULTS

In the 'cut-through' group, eight patients who had a blade exchanges (50%) and two patients with blade exchange and augmentation (33%) required further revision operations. THA was the definite treatment in all 6 cases. In the 'cut-out' group, two patients (66%) who had blade exchanges and two (66%) who underwent re-nailing required additional revision operations during the subsequent course. One patient (4%) who had total hip arthroplasty needed revision surgery for acetabular replacement. Overall, a total of 81 revision procedures were performed.

CONCLUSION

Based on the data from this study, we recommend THA as the only valid salvage procedure for 'cut-out' and 'cut-through' of helical blades after fixation of trochanteric fractures with the PFNA and TFN.

The Effectiveness of Corticosteroid Injection for De Quervain's Stenosing Tenosynovitis (DQST): A Systematic Review and Meta-Analysis

De Quervain's stenosing tenosynovitis (DQST) treatments include corticosteroid injection around the tendon sheath; however there is some ambiguity concerning the efficacy of this treatment. The aim of this systematic review and meta-analysis is to examine the totality of evidence relating to the use of corticosteroid injection in DQST when compared to placebo or other active treatments. A systematic literature search was conducted in July 2014. Only randomized control trials (RCTs) were included. Outcome measures included impairment, activity limitation and participation restriction. Five RCTs were identified with 165 patients, 88 in the treatment group and 77 in the control group.Patients who received corticosteroid injection (n=142) had a higher rate of resolution of symptoms [RR 2.59, 95% CI: 1.25 to 5.37, p=0.05, I2=62%]. This group reported greater pain relief as assessed by Visual Analogue Scale (VAS) at first assessment [mean difference -2.51, 95% CI: -3.11 to -1.90, p=0.0003, I2=65%] and demonstrated a statistically significant improvement in function (n=78) as measured by the DASH score and Dutch AIMS-HFF score [SMD -0.83, 95% CI: -1.54 to -0.12, p=0.02, I2=48]. This review confirms that corticosteroid injection results in a statistically significant increase in resolution of symptoms, pain relief and increased function in the treatment of DQST.

Intramedullary nailing of trochanteric fractures: central or caudal positioning of the load carrier? A biomechanical comparative study on cadaver bones

BACKGROUND

Current recommendations with regard to central or caudal positioning of the femur head carrier in the management of trochanteric fractures are contradictory.

METHODS

A standardised pertrochanteric osteotomy was stabilised in 15 pairs of cadaver femurs by means of intramedullary osteosynthesis (5xPFN-A-Synthes, 5xIntertan-Smith&Nephew, 5xTargon-PF-Aesculap). For each pair randomised central (group A) or caudal (group B) implantation of the femoral neck component was performed. Subsequently, the constructs were axially loaded to 2100N. In the absence of cut out after 20,000 cycles, load was increased to a maximum force of 3100N. Angular displacement was recorded based on ultrasound. Migration of the load carrier in the femoral head was monitored radiologically.

FINDINGS DISPLACEMENT

No significant difference between groups (p>0.15) was found for the first 50 load cycles. A significantly greater degree of varus deformity was observed in group A (p=0.049) after 2000 load cycles and became more apparent as the number of load cycles increased (after 6000 cycles p=0.039, after 20,000 cycles p=0.034, after 22,000 cycles p=0.016). Angular displacement in the other two planes did not differ significantly across groups. CUT OUT: Migration of the load carrier in the femoral head was not significantly different for the two groups. Overall cut out occurred in 9 constructs, 3 in group A and 6 in group B. The difference in cut-out rate was not significant (p=0.213, chi-squared test).

CONCLUSION

Biomechanical superiority can be shown for caudal positioning of the femoral neck load carrier in terms of reduced varus deformity. The incidence of cut out is however unaffected by the position of the load carrier.

Rotationally stable screw-anchor versus sliding hip screw plate systems in stable trochanteric femur fractures: a biomechanical evaluation

OBJECTIVES

The rotationally stable screw-anchor plate system (RoSA) is unique in using a novel screw-blade combination. This investigation tested the hypothesis whether RoSA is advantageous over the sliding hip screw plate system (SHS) with regard to stiffness, failure load, displacement, and migration in stable trochanteric femur fractures (OTA 31A1.1).

METHODS

Thirteen femur pairs (mean age = 79 years; range, 64-92 years) received implants of either the RoSA or SHS (Koenigsee Implants, Allendorf, Germany). Beginning with 300 N and under consecutive 300 N load-increase steps (2000 cycles, 0.5 Hz) the femurs were cycled until failure. Specimens were evaluated for fragment displacement in both frontal and rotational planes and for migration. A survival analysis was carried out.

RESULTS

With regard to stiffness (526 ± 195 N/mm vs 358 ± 143 N/mm; P = 0.006) and the failure load (2838 ± 781 N vs 2262 ± 863 N; P = 0.012), the RoSA proved superior to the SHS. Furthermore, RoSA demonstrated higher rotational stability in comparison to the SHS (1800 N: 0 ± 0 degrees vs 1.1 ± 1.3 degrees; P = 0.015; failure point: 0 ± 0 degrees vs 2.3 ± 2.6 degrees; P = 0.008), measuring rotation about femoral neck axis over time. Whereas cutout occurred only in the RoSA system (n = 3; P = 0.110), the SHS underwent plastic deformation in 7 cases (n = 7; P = 0.003). In one case (7%), the insertion of the RoSA blade resulted in iatrogenic cut-through caused by a jamming of the screw and the blade.

CONCLUSIONS

The fixation of stable trochanteric femur fractures with RoSA in cadavers led to greater primary stability under cyclic load, with significant advantages with regard to stiffness, failure load, and rotational stability, compared with the SHS. A detrimental effect was its migration tendency, which began at 1800 N and occurred in the cranial direction. A meticulous insertion technique was a prerequisite to avoid iatrogenic perforation of the femoral head. Our results will have to be substantiated by further biomechanical and clinical trials using an optimized RoSA system.

Dynamic hip screw blade fixation for intertrochanteric hip fractures

PURPOSE

To assess the one-year outcome of a dynamic hip screw (DHS) blade in the treatment of AO/OTA 31-A1 and 31-A2 intertrochanteric hip fractures.

METHODS

35 men and 65 women aged 47 to 100 (mean, 83) years underwent fixation with a DHS blade for A1 (n=47) and A2 (n=53) intertrochanteric hip fractures after a low-energy injury. Patients were operated on within 48 hours of admission. Anteroposterior and lateral radiographs were examined for the tip-apex distance and femoral shortening. Potential complications were looked for, including implant migration, cut-out, loosening, or breakage. Functional outcome was based on the Parker mobility score.

RESULTS

The 30-day and one-year mortality rates were 5% and 20%, respectively. At the one-year follow-up, 81 patients were available, and all fractures had healed without varus deformity. The mean tip-apex distance was 14.1 (range, 5.7-31.1; SD, 4.3) mm. The mean femoral shortening was 4.9 (range, 0-20.2; SD, 4.8) mm. The mean Parker score decreased to 3.8 at one-year follow-up from 5.9 before injury (p<0.001). There was one loss of fixation secondary to a non-traumatic subcapital fracture at 3 months, for which a bipolar hemiarthroplasty was performed. CONCLUSION; The DHS blade system is effective in treating AO/OTA 31-A1 and 31-A2 intertrochanteric hip fractures and results in a low complication rate.

Outcome of short proximal femoral nail antirotation and dynamic hip screw for fixation of unstable trochanteric fractures. A randomised prospective comparative trial

A prospective, randomised, controlled trial was performed to compare the outcome of treatment of unstable trochanteric fractures with either a short proximal femoral nail antirotation (PFNA) or dynamic hip screw (DHS). Eighty one patients with unstable fracture of the proximal part of the femur were randomised, at the time of admission, for fixation with either a short PFNA (n=42) or DHS (n= 39). The primary outcome measure was reoperation within the first postoperative year and mortality at the end of one year. Operative time, fluoroscopy time, blood loss, and any intra-operative complication were recorded for each patient. Clinical and radiological follow-up was undertaken for a minimum of 36 months. Any changes in the position of the implant or fixation failure were recorded. Hip range of motion, pain in the hip or thigh and return to work were used to compare the outcomes. There was no significant difference between 1 year mortality rates for the two groups. The mean operative time was significantly less in PFNA group (25 min) than in the DHS group (38 min). Patients treated with a PFNA experienced a shorter fluoroscopy time and less blood loss. Six patients in DHS group had implant failure while none experienced this in PFNA group. The PFNA group had a better functional outcome than the DHS group.

Is the rotation of the femoral head a potential initiation for cutting out? A theoretical and experimental approach

Background

Since cut-out still remains one of the major clinical challenges in the field of osteoporotic proximal femur fractures, remarkable developments have been made in improving treatment concepts. However, the mechanics of these complications have not been fully understood.

We hypothesize using the experimental data and a theoretical model that a previous rotation of the femoral head due to de-central implant positioning can initiate a cut-out.

Methods

In this investigation we analysed our experimental data using two common screws (DHS/Gamma 3) and helical blades (PFN A/TFN) for the fixation of femur fractures in a simple theoretical model applying typical gait pattern on de-central positioned implants. In previous tests during a forced implant rotation by a biomechanical testing machine in a human femoral head the two screws showed failure symptoms (2-6Nm) at the same magnitude as torques acting in the hip during daily activities with de-central implant positioning, while the helical blades showed a better stability (10-20Nm).

To calculate the torque of the head around the implant only the force and the leverarm is needed (N [Nm] = F [N] * × [m]). The force F is a product of the mass M [kg] multiplied by the acceleration g [m/s²]. The leverarm is the distance between the center of the head of femur and the implant center on a horizontal line.

Results

Using 50% of 75 kg body weight a torque of 0.37Nm for the 1 mm decentralized position and 1.1Nm for the 3 mm decentralized position of the implant was calculated. At 250% BW, appropriate to a normal step, torques of 1.8Nm (1 mm) and 5.5Nm (3 mm) have been calculated.

Comparing of the experimental and theoretical results shows that both screws fail in the same magnitude as torques occur in a more than 3 mm de-central positioned implant.

Conclusion

We conclude the center-center position in the head of femur of any kind of lag screw or blade is to be achieved to minimize rotation of the femoral head and to prevent further mechanical complications.

Side plate fixation vs. intramedullary nailing in an unstable medial femoral neck fracture model: A comparative biomechanical study

BACKGROUND

The objective of this study was to investigate primary stability of the proximal femoral nailing antirotation for the indication of unstable medial femoral neck fractures. The device was compared to the dynamic hip screw blade, which is a "gold standard" in the treatment of proximal femoral fractures.

METHODS

Six pairs of human cadaver femurs were tested in a cyclic loading model with loads up to 200 N, 400 N, 600 N, 800 N, and 1000 N, respectively. Iliotibial tract was simulated by a chain that applied forces on the greater trochanter during loading. In vitro combined axial and bending loads were applied. Angular displacements during loading were recorded in all directions, and loads to failure were recorded.

FINDINGS

For the cyclic loading test no statistically significant differences between the two groups could be detected. Specimens fixed with the dynamic hip screw blade showed higher displacements in the varus direction at 400 N and 600 N, in the external rotation at 200 N, 400 N and 600 N, and in the anterior direction at 400 N. Load to failure revealed no statistical difference between the two implants.

INTERPRETATION

The proximal femoral nailing antirotation achieves primary stability comparable to the dynamic hip screw blade. The proximal femoral nailing antirotation combines the biomechanical favorable concept of intramedullary fixation with a minimally invasive surgical technique, which theoretically may be advantageous in clinical use. Further biomechanical studies are required to clarify to what extent the results of the present study can be transferred to the clinical situation.

The dynamics of proximal femoral nails: a clinical comparison between PFNA and Targon PF

The objective of this study comparing the proximal femoral nails Targon PF (Aesculap, Tuttlingen, Germany) and Proximal Femoral Nail Antirotation (PFNA; Synthes. Oberdorf, Switzerland) was to observe the complications and postoperative results following pertrochanteric femoral fracture fixation, with special attention devoted to the dynamic properties of both implants under physiological load in vivo. The survey was designed as a randomized, prospective study of 80 patients who had sustained a pertrochanteric femoral fracture (AO type 31.A2). Postoperative radiological and clinical examinations were conducted over a period of 12 months on 40 respective patients treated with a PFNA or a Targon PF nail. Average operative time was 66.2 minutes and average fluoroscopy time was 103.6 seconds in the PFNA group, which was significantly lower than in the Targon PF group (84.7 minutes and 164.5 seconds, respectively). No significant difference was found between the 2 groups in terms of range of motion (P=.26) or Harris Hip Score (P=.83). The femoral neck components of the Targon PF showed a significantly higher sliding ability (14.5 mm; P=.04) than the PFNA (11.1 mm).Both implants are suited to treat pertrochanteric femoral fractures and display comparable clinical results. The Targon PF demonstrates better dynamic properties than the PFNA under physiological load in vivo. A disadvantage of the Targon PF, however, is the more complicated surgical technique and the longer operative time.

Ipsilateral basicervical femoral neck and shaft fractures treated with long proximal femoral nail antirotation or various plate combinations: comparative study

BACKGROUND

Although many treatment methods have been developed, controversy exists regarding the optimal management of ipsilateral femoral neck and shaft fractures. The purpose of this retrospective study was to compare the results of long proximal femoral nail antirotation (PFNA-long) and various plate combinations in the treatment of ipsilateral basicervical femoral neck and shaft fractures.

METHODS

Between January 2004 and May 2008, a total of 21 patients with ipsilateral basicervical femoral neck and shaft fractures were treated with PFNA-long or various plate combinations. We divided patients into two groups. Group I included 11 patients who underwent surgery with cancellous lag screws or dynamic hip screws (DHS) combined with compression plate fixation. Group II included 10 patients who underwent surgery with PFNA-long.

RESULTS

The average follow-up periods were 22.2 and 20.8 months for groups I and II, respectively. The average union times for femoral neck fractures in groups I and II were 15.6 and 16.0 weeks, respectively; and the average union times for shaft fractures were 21.1 and 20.3 weeks, respectively. There were eight good, two fair, and one poor functional result in group I and eight good, one fair, and one poor in group II. One case of implant failure and nonunion of the femoral shaft fracture occurred in group I. There were no significant differences in the functional outcomes or major complications between the two groups.

CONCLUSIONS

Both treatment methods achieved satisfactory functional outcomes in patients with ipsilateral basicervical femoral neck and shaft fractures. PFNA-long was a good option for the treatment of complex fractures, with the advantages of closed antegrade nailing with minimal exposure, reduced perioperative blood loss, and biological fixation of both fractures with a single implant.

Medial migration of lag screw with intrapelvic dislocation in gamma nailing--a unique problem? A report of 2 cases

Within the last decade, intramedullary nailing systems have gained popularity in the treatment of unstable fractures of the trochanteric region with good clinical results. However, these implants are not free of complications. Commonly reported treatment failures include implant cutout through the femoral neck, stress-derived femur fractures at the distal end of the nail, and secondary rotational displacement and varus deformity of the femoral neck and head. Only few reports exist on primary medial migration of the lag screw after treatment with intramedullary implants. We report on a rarely described complication in 2 patients who underwent osteosynthesis with a Gamma 3 nail (Stryker, Mahwah, NJ). Both patients presented with implant failures due to primary medial migration of the lag screw. Complete separation of the implant occurred, and the lag screw penetrated through the acetabulum into the pelvis. The patient's histories and course of treatment are reported. The literature on this topic is discussed.

A comparative study of screw and helical proximal femoral nails for the treatment of intertrochanteric fractures

The goal of this study was to compare treatment outcomes of screw proximal femoral nails and helical proximal femoral nails and to investigate the effectiveness of helical proximal femoral nails for the treatment of intertrochanteric fractures. Forty patients with intertrochanteric fractures were treated at our institution between January 2005 and January 2007, with a minimum follow-up of 1.5 years. Seventeen patients were treated with screw proximal femoral nails (mean patient age, 67 years; age range, 45-89 years; men:women ratio, 3:14), and 23 were treated with helical proximal femoral nails (mean patient age, 74 years; age range, 64-91 years; men:women ratio, 6:17). We evaluated mean operation time, amount of bleeding, time to ambulation, average union period, changes in neck shaft angle, and complications, and performed radiographic reviews, telephone interviews, and direct contact interviews at an outpatient clinic. We evaluated postoperative function and mobility using social function scores and mobility scores.Helical proximal femoral nails produced better results in terms of social function scores, mobility scores, and complication rates with statistical significance. No significant differences were found between the 2 nails in terms of mean operation time, amount of bleeding, average union period, time to ambulation, or neck shaft angle changes. Screw proximal femoral nails and helical proximal femoral nails are suitable implants for intertrochanteric fractures, but helical proximal femoral nails are better in terms of functional aspects and complication rates.

Is a helical shaped implant a superior alternative to the Dynamic Hip Screw for unstable femoral neck fractures? A biomechanical investigation

BACKGROUND

The Dynamic Hip Screw is well established for the treatment of femoral neck fractures. However, cut-out occurs in 1-6% of all cases. This study compared the biomechanical performance of a helical shaped implant (DHS-Blade) to the Dynamic Hip Screw in an unstable femoral neck fracture model.

METHODS

Ten pairs of human cadaveric femora were either instrumented with a DHS-Blade or a Dynamic Hip Screw. Osteotomies were created using a custom-made saw-guide. Cyclic loading was performed by introducing in vivo measured load-trajectories to the femoral head. Starting at 1500 N, the load was stepwise increased until failure of the construct. Radiographs were taken in 5000 cycles increments to identify onset of femoral head migration with respect to the implant. A survival analysis was performed on the cycles to onset of migration. A paired t-test was carried out on the displacements of the femoral head relative to the shaft as determined by optical motion tracking.

FINDINGS

One hundred percent migrations occurred for the Dynamic Hip Screw compared to 50% for the DHS-Blade. The survival probability in terms of implant anchorage was found higher for the blade (P=0.023). However, significant higher deformation of the repair construct was observed for the DHS-Blade (P=0.004).

INTERPRETATION

The study showed superior implant anchorage of the DHS-Blade compared to the DHS, which might reduce the cut-out risk. Nevertheless, the blade allowed higher deformation of the femur mainly resulting in shortening of the neck, which might be due to a systematic loss of fracture reduction.

The new proximal femoral nail antirotation (PFNA) in daily practice: results of a multicentre clinical study

The treatment of unstable trochanteric femoral fractures is still challenging. The ideal implant should be easy to handle, allow for immediate full weight-bearing postoperatively and should have sufficient purchase in the femoral head/neck-fragment to limit cut-outs due to varus-deviation and rotation. The proximal femoral nail antirotation (PFNA), designed by AO, is an intramedullary device with a helical blade rather than a screw for better purchase in the femoral head and was tested in a clinical study. Consecutive patients with unstable trochanteric fractures (AO-classification 31.A.2 and A.3 only) were included and followed for 1 year. Primary objectives were assessment of operative and postoperative complications, whereas secondary objectives included surgical details, general complications and final outcome measurements. In 11 European clinics, 315 patients were included and treated with a PFNA. Almost all fractures healed within 6 months. Fifty-six percent of the patients regained the pre-trauma mobility and 18% died within the follow-up period. Forty-six implant-related complications--leading to 28 unplanned re-operations--were recorded, with four acetabular penetrations (three of which were after a new fall on that hip) and seven ipsilateral femoral shaft fractures as the most serious ones. As the joint-penetrations did not resemble the cut-out seen with other implants it is concluded that the PFNA--due to its helical blade--possibly limits the effects of early rotation of the head/neck-fragment in unstable trochanteric fractures and therefore seems currently to be the optimal implant for the treatment of these fractures especially in osteoporotic bone.